Heavy metal concentrations in the tissues of the Black-headed Gull Larus ridibundus L. nesting in the dam reservoir in south-western Poland

Concentrations of heavy metals (lead, cadmium and copper) were measured in several tissues (pectoral muscle, liver, kidney, lung, femur, brain and feather) of the fledglings and adults of black-headed gull Larus ridibundus L. collected in breeding colony (c. 2000 pairs) in south-western Poland (Mietkowski Reservoir; 980 ha). Fourteen birds (5 fledglings and 9 adults) were collected shortly after death (unknown reason of mortality) in June and July 2003. The highest mean ([plus or minus] 1 SD) level of lead was demonstrated in femur samples (42.32 [plus or minus] 31.42 [micro-]g g[^-1] dry weight), whistle the lowest one, in muscle (3.59 [plus or minus] 0.57 [micro-]g g[^-1] d.w.). The highest and the lowest levels of cadmium were in turn demonstrated in kidney (5.51 [plus or minus] 4.90 [micro-]g g[^-1] d.w.) and in muscle (0.31 [plus or minus] 0.22 [micro-]g g[^-1] d.w.), respectively. Liver was the organ with the highest copper accumulation (29.22 [plus or minus] 13.56 [micro-]g g[^-1] d.w.), whereas the lowest amounts of the element were found in femur samples (2.79 [plus or minus] 1.01 [micro-]g g[^-1] d.w.). Among 21 pairs of tissues in which metal concentrations were compared, only in eight cases statistically significant differences between fledglings and adults were recorded. The accumulation of heavy metals in organs of black headed gull was up to c. 81-fold lower than in bottom sediments of this reservoir.